Veterinarija ir Zootechnika

Koi carp (Cyprinus carpio var. koi) are globally popular ornamental fish, valued for their distinctive coloration and patterns. However, infectious disease outbreaks remain an important health concern, particularly bacterial infections associated with skin ulceration, systemic disease, and mortality. Motile aeromonad infections in freshwater fish, including koi carp, have traditionally been attributed mainly to Aeromonas hydrophila, while other species may have been underdiagnosed or overlooked. In this report, we describe the isolation of Aeromonas veronii from koi carp in a private collection presenting with lesions consistent with koi ulcer disease, together with the associated macroscopic findings.